When biosolid fertilizer is pressed through specially designed dye plates, the friction of the process produces heat. At the proper temperature, the naturally occurring lignen in the biosolids is released to help in the formation of the pellet. Lignen is a complex organic polymer found in the tissue of most plants, therefore it is naturally present in biosolids. 
When Class A, exceptional quality (EQ) biosolids are produced using a drying or thermal process, the end product can often contain varying amounts of dust. A dusty product can create issues related to uneven spreading patters, drifting and improper  nutrient placement.